A comparative study of the geochemical and mineralogical characteristics of the S1 sapropel in the western and eastern Mediterranean

Sapropels, which are dark sediments with organic carbon content > 2 wt%, are common in eastern Mediterranean sections. In some western Mediterranean sites, however, even organic-rich layers (ORLs) are not detected in sections spanning the S1 sapropel deposition event (9500-6000 yr BP). We compare geochemical and mineralogical compositions in cores from the eastern (Ionian Sea) and western (Alboran Sea and South Balearic basin) Mediterranean basins to determine the causes for the lack of ORL deposition during S1 in the western basin. In particular, we investigate whether the differences between the eastern and western sites are due to preservation or productivity variations. Using mineralogical and geochemical data - mineral abundances, major and trace element concentrations and ratios, organic carbon content, Ba and barite accumulations, and sea surface temperature data along with information about the sedimentary regimes, sedimentation rates, and water depths at these sites, we conclude that the lack of S1 sapropel formation in the western Mediterranean is due to lower export production fluxes in this basin. Accordingly, the response to regional climate changes through time must be different in the eastern and western Mediterranean. Identifying the exact causes for these differences may lead to an understanding of the variations in export production rates in response to basin-wide versus regional climate changes in the Mediterranean region. (C) 2002 Elsevier Science B.V. All rights reserved.